Short-Period Small Planets with High Mutual Inclinations are more Common around Metal-Rich Stars
We present a correlation between the stellar metallicities and the mutual inclinations of multi-planet systems hosting short-period small planets (a/Rs<12, Rp<4Re). We analyzed 89 multi-planet systems discovered by Kepler, K2, and TESS, where the innermost planets have periods shorter than 10 days.
We found that the mutual inclinations of the innermost two planets are higher and more diverse around metal-rich stars. The mutual inclinations are calculated as the absolute differences between the best-fit inclinations of the innermost two planets from transit modeling, which represent the lower limits of the true mutual inclinations.
The mean and variance of the mutual inclination distribution of the metal-rich systems are 3.1+-0.5 and 3.1+-0.4 degrees, while for the metal-poor systems they are 1.3+-0.2 and 1.0+-0.2 degrees. This finding suggests that inner planetary systems around metal-rich stars are dynamically hotter.
We summarized the theories that could plausibly explain this correlation, including the influence of giant planets, higher solid densities in protoplanetary disks around metal-rich stars, or secular chaos coupled with an excess of angular momentum deficits. Planet formation and population synthesis models tracking the mutual inclination evolution would be essential to fully understand this correlation.
String plot for the 89 planetary systems in this work, with system names labeled on the left. Host stars are sorted and color-coded based on their [Fe/H] values, with more metal-rich stars plotted on top with warmer colors. The background grids are shaded according to mutual inclinations, ∆i, where darker shades correspond to higher values. The sizes of the star and planet symbols are scaled by their radii. [Fe/H] and ∆i values used to create this figure are listed in Table 1, while other parameters are from the NEA. — astro-ph.EP
Xinyan Hua, Sharon Xuesong Wang, Dongsheng An, Songhu Wang, Yang Huang, Dichang Chen, Johannes Buchner, Wei Zhu, Fei Dai, Jiwei Xie
Comments: 14 pages, 5 figures, 1 table. Accepted by ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2502.00442 [astro-ph.EP] (or arXiv:2502.00442v2 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2502.00442
Focus to learn more
Submission history
From: Xinyan Hua
[v1] Sat, 1 Feb 2025 14:21:59 UTC (1,347 KB)
[v2] Tue, 4 Feb 2025 06:34:04 UTC (1,347 KB)
https://arxiv.org/abs/2502.00442
Astrobiology
